Self-limiting electrical triggering for initiating fracture of frangible glass

Abstract

A transient electronic device includes electronic elements (e.g., an SOI- or chip-based IC) and a trigger mechanism disposed on a frangible glass substrate. The trigger mechanism includes a switch that initiates a large trigger current through a self-limiting resistive element in response to a received trigger signal. The self-limiting resistive element includes a resistor portion that generates heat in response to the trigger current, thereby rapidly increasing the temperature of a localized (small) region of the frangible glass substrate, and a current limiting portion (e.g., a fuse) that self-limits (terminates) the trigger current after a predetermined amount of time, causing the localized region to rapidly cool down. The frangible glass substrate is engineered such that a stress profile produced by the rapid heating/cooling of the localized region generates an initial fracture force that subsequently propagates throughout the glass substrate, whereby sufficient potential energy is released to powderize the electronic elements.

The invention claimed is: 
     
       1. A transient electronic device, comprising:
 a frangible glass substrate; and 
 a trigger mechanism comprising:
 a self-limiting resistive element comprising a material disposed over a localized region of the frangible glass substrate, the self-limiting resistive element configured such that: 
 during a time period when a current from a power source flows through the self-limiting resistive element, heat generated by the self-limiting resistive element increases a localized temperature of the localized region from an initial temperature toward a first temperature level; and 
 a current-limiting portion of the self-limiting resistive element is configured to control the flow of a trigger current such that the trigger current flow is terminated when the localized temperature of the localized region increases to the first temperature level, thereby causing the localized temperature to decrease from the first temperature level to a second temperature level; 
 
 wherein the frangible glass substrate is configured such that the localized temperature increase and the localized temperature decrease causes the frangible glass substrate to fracture. 
 
     
     
       2. The device of  claim 1 , wherein the current-limiting portion comprises an electronic circuit configured to terminate the flow of the trigger current. 
     
     
       3. The device of  claim 1 , wherein the current-limiting portion comprises a thermistor-based circuit configured to terminate the flow of the trigger current in response to detecting the first temperature level. 
     
     
       4. The device of  claim 1 , wherein the current-limiting portion comprises a timer-based circuit configured to terminate the flow of the trigger current after a preset time following initiation of the flow of the trigger current. 
     
     
       5. The device of  claim 1 , wherein the self-limiting resistive element comprises resistive structures, and the resistive structures and the current-limiting portion comprise two or more different materials with different melting points and different electrical conductivity. 
     
     
       6. The device of  claim 1 , wherein:
 the self-limiting resistive element comprises resistive structures; 
 the current-limiting portion is rectangular in shape; and 
 a width of the current-limiting portion is different from a widest dimension of the resistive structures. 
 
     
     
       7. The device of  claim 1 , wherein the current-limiting portion comprises a fuse element. 
     
     
       8. The device of  claim 7 , wherein the fuse element has a meandering shape. 
     
     
       9. The device of  claim 1 , wherein:
 the triggering mechanism further comprises a sensor configured to detect a predetermined light, temperature, acoustic or radio wave signal; and 
 the triggering mechanism is configured to activate the power source in response to detecting the predetermined signal. 
 
     
     
       10. A method of fracturing a transient electronic device, comprising:
 during a time period when a current from a power source flows through a self-limiting resistive element disposed over a localized region of a frangible glass substrate, generating heat by the self-limiting resistive element to increase a localized temperature of the localized region from an initial temperature toward a first temperature level; 
 controlling the flow of a trigger current by a current-limiting portion of the self-limiting resistive element such that the trigger current flow is terminated when the localized temperature of the localized region increases to the first temperature level, thereby causing the localized temperature to decrease from the first temperature level to a second temperature level; and 
 fracturing the frangible glass substrate in response to the increase and decrease in the localized temperature. 
 
     
     
       11. The method of  claim 10 , wherein:
 the current-limiting portion comprises an electronic circuit; and 
 the method further comprises terminating the flow of the trigger current by the electronic circuit. 
 
     
     
       12. The method of  claim 10 , wherein:
 the current-limiting portion comprises a thermistor-based circuit; and 
 the method further comprises terminating the flow of the trigger current by the thermistor-based circuit in response to detecting the first temperature level. 
 
     
     
       13. The method of  claim 10 , wherein:
 the current-limiting portion comprises a timer-based circuit; and 
 the method further comprises terminating the flow of the trigger current by the timer-based circuit after a preset time following initiation of the flow of the trigger current. 
 
     
     
       14. The method of  claim 10 , wherein:
 the current-limiting portion comprises a fuse element; and 
 the method further comprises terminating the flow of the trigger current in response to melting or breaking of the fuse element. 
 
     
     
       15. The method of  claim 14 , wherein the fuse element has a meandering shape. 
     
     
       16. The method of  claim 10 , wherein the triggering mechanism further comprises a sensor, and the method further comprises:
 detecting, by the sensor, a predetermined light, temperature, acoustic or radio wave signal; and 
 activating the power source in response to detecting the predetermined signal. 
 
     
     
       17. A transient electronic device, comprising:
 a frangible glass substrate; 
 one or more electronic elements disposed on the frangible glass substrate; and 
 a trigger mechanism comprising:
 a self-limiting resistive element comprising a material disposed over a localized region of the frangible glass substrate, the self-limiting resistive element configured such that: 
 during a time period when a current from a power source flows through the self-limiting resistive element, heat generated by the self-limiting resistive element increases a localized temperature of the localized region from an initial temperature toward a first temperature level; and 
 a current-limiting portion of the self-limiting resistive element is configured to control the flow of a trigger current such that the trigger current flow is terminated when the localized temperature of the localized region increases to the first temperature level, thereby causing the localized temperature to decrease from the first temperature level to a second temperature level; 
 
 wherein the frangible glass substrate is configured such that the localized temperature increase and the localized temperature decrease causes the frangible glass substrate to fracture. 
 
     
     
       18. The device of  claim 17 , wherein the current-limiting portion comprises an electronic circuit configured to terminate the flow of the trigger current. 
     
     
       19. The device of  claim 17 , wherein the current-limiting portion comprises a thermistor-based circuit configured to terminate the flow of the trigger current in response to detecting the first temperature level. 
     
     
       20. The device of  claim 17 , wherein the current-limiting portion comprises a timer-based circuit configured to terminate the flow of the trigger current after a preset time following initiation of the flow of the trigger current. 
     
     
       21. The device of  claim 17 , wherein the current-limiting portion comprises a fuse element. 
     
     
       22. The device of  claim 21 , wherein the fuse element has a meandering shape.